So what is UV ink? It’s a special tattoo ink that only glows under ultraviolet light or blacklight. These special inks for black light tattoos contain chemicals that absorb the high energy UV rays for a few nanoseconds. Then the chemicals release the energy and the tattoo glows! There are many different colors of black light or UV reactive ink. For the titanium white color, in the absence of UV light, the tattoo can be completely transparent on light skin tones. Other colors are visible in any light but glow in black light!
Here are some cool examples I found over the web of what you could do with them: